The blast targeted a mosque located next to local police headquarters in the Lower Dir region.
Hospital officials say at least 28 people were wounded in the bombing, including several children.
Lower Dir lies next to Swat Valley, the site of a fierce military offensive earlier this year to the oust the Taliban. Militants have since retaliated with a series of attacks targeting security forces in the area.
In other violence, Pakistani intelligence officials say a suspected U.S. drone attack has killed three militants in the country's northwest.
Officials say the drone fired missiles at a house in North Waziristan Friday, killing three militants and wounding two others.
The attack, was the third by a suspected U.S. drone since Thursday.
Some information for this report was provided by AP and AFP.